linux-kernel - [PATCH v3 20/75] x86/boot/compressed/64: Call set_sev_encryption

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Message-Id: <20200428151725.31091-21-joro@8bytes.org>
Date:   Tue, 28 Apr 2020 17:16:30 +0200
From:   Joerg Roedel <joro@...tes.org>
To:     x86@...nel.org
Cc:     hpa@...or.com, Andy Lutomirski <luto@...nel.org>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Thomas Hellstrom <thellstrom@...are.com>,
        Jiri Slaby <jslaby@...e.cz>,
        Dan Williams <dan.j.williams@...el.com>,
        Tom Lendacky <thomas.lendacky@....com>,
        Juergen Gross <jgross@...e.com>,
        Kees Cook <keescook@...omium.org>,
        David Rientjes <rientjes@...gle.com>,
        Cfir Cohen <cfir@...gle.com>,
        Erdem Aktas <erdemaktas@...gle.com>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        Mike Stunes <mstunes@...are.com>,
        Joerg Roedel <joro@...tes.org>, Joerg Roedel <jroedel@...e.de>,
        linux-kernel@...r.kernel.org, kvm@...r.kernel.org,
        virtualization@...ts.linux-foundation.org
Subject: [PATCH v3 20/75] x86/boot/compressed/64: Call set_sev_encryption_mask earlier

From: Joerg Roedel <jroedel@...e.de>

Call set_sev_encryption_mask() while still on the stage 1 #VC-handler,
because the stage 2 handler needs our own page-tables to be set up, to
which calling set_sev_encryption_mask() is a prerequisite.

Signed-off-by: Joerg Roedel <jroedel@...e.de>
---
 arch/x86/boot/compressed/head_64.S      | 8 +++++++-
 arch/x86/boot/compressed/ident_map_64.c | 3 ---
 2 files changed, 7 insertions(+), 4 deletions(-)

diff --git a/arch/x86/boot/compressed/head_64.S b/arch/x86/boot/compressed/head_64.S
index af571127c9ba..940d44149a29 100644
--- a/arch/x86/boot/compressed/head_64.S
+++ b/arch/x86/boot/compressed/head_64.S
@@ -534,9 +534,15 @@ SYM_FUNC_START_LOCAL_NOALIGN(.Lrelocated)
 	rep	stosq
 
 /*
- * Load stage2 IDT and switch to our own page-table
+ * If running as an SEV guest, the encryption mask is required in the
+ * page-table setup code below. When the guest also has SEV-ES enabled
+ * set_sev_encryption_mask() will cause #VC exceptions, but the stage2
+ * handler can't map its GHCB because the page-table is not set up yet.
+ * So set up the encryption mask here while still on the stage1 #VC
+ * handler. Then load stage2 IDT and switch to our own page-table.
  */
 	pushq	%rsi
+	call	set_sev_encryption_mask
 	call	load_stage2_idt
 	call	initialize_identity_maps
 	popq	%rsi
diff --git a/arch/x86/boot/compressed/ident_map_64.c b/arch/x86/boot/compressed/ident_map_64.c
index 83385a551f01..6ee089fdc65a 100644
--- a/arch/x86/boot/compressed/ident_map_64.c
+++ b/arch/x86/boot/compressed/ident_map_64.c
@@ -107,9 +107,6 @@ static void add_identity_map(unsigned long start, unsigned long end)
 /* Locates and clears a region for a new top level page table. */
 void initialize_identity_maps(void)
 {
-	/* If running as an SEV guest, the encryption mask is required. */
-	set_sev_encryption_mask();
-
 	/* Exclude the encryption mask from __PHYSICAL_MASK */
 	physical_mask &= ~sme_me_mask;
 
-- 
2.17.1